The present invention relates to a layered absorbent structure. More particularly, the invention relates to a layered, composite absorbent structure with individual layers which are constructed and arranged to selectively cooperate to provide desired performance parameters in the composite, layered structure.
Performance objectives of disposable absorbent articles, such as infant diapers, include no product leakage, dry feel to the wearer, and a comfortable fit throughout the product life. Accordingly, absorbent articles typically contain an absorbent core to provide liquid handling and other absorbent functionalities required to meet the product performance objectives. The absorbent core of absorbent articles is commonly composed of wood pulp fibers, and superabsorbent material is often distributed in the absorbent core to enhance the liquid absorbent capacity. The absorbent core is usually formed in an hourglass, T-shaped, or similar configuration with reduced absorbent width in the central crotch region for wearer fit and comfort.
Absorbent articles frequently leak before the liquid absorbent capacity of the entire absorbent core is fully utilized. One problem resulting in leakage is the inability of the absorbent core to fully uptake liquids rapidly and completely when large amounts of liquids are discharged into the absorbent article. Another associated problem contributing to leakage is the inability of the absorbent core to move or distribute sufficient amounts of liquid between discharges from a target area portion of the absorbent article to more distal and more remote end regions of the absorbent core which have not been utilized. This results in saturation of only the central target area of the absorbent core and excessive thickness, bulkiness, and sagging of the wet, heavy absorbent material resulting in poor performance, product fit and wearer discomfort. These absorbent core deficiencies are especially acute for thin, narrower-crotch absorbent designs having a crotch width of less than about 4 inches that provides less absorbent mass and bulk in the target area for improved product fit.
The absorbent core of current absorbent articles does not adequately meet current performance objectives. The desirable absorbent core liquid uptake and distribution functionalities required for upstream narrower crotch higher efficiency absorbent article designs is also beyond current capabilities. Consequently, there remains a need for absorbent structures which can provide improved fluid uptake of liquid insults and improved liquid distribution to move liquid out of the target area between liquid insults to maintain this desirable liquid uptake behavior for the life of the product.
The disclosed invention is an absorbent system which includes multiple absorbent layer regions. The two or more absorbent layer regions can advantageously interact in a manner which preferentially locates an appointed liquid in a selected layer region. This localization of the liquid within this layer region can increase the potential of this layer region to move liquid through capillary action due to the higher saturation level and increased amount of liquid available. The intake capability of the absorbent system can be maintained or improved over current systems by keeping a layer region of the absorbent system at low saturation levels through as many insults of the product as possible, while providing optimum intake performance through appropriate control of the composite properties. The low saturation in this layer region provides void volume for the incoming insult as well as a high permeability, thus increasing the intake rate of the absorbent system as a whole. The properties of this layer region can advantageously be balanced with an appropriately high level of capillary tension to provide enough control of the liquid to substantially stop undesired leakage. This low saturation layer region can be used in addition to a layer of surge management material and can provide an intake functionality in addition to that provided by the surge material. In particular aspects of the invention, a body side layer of the absorbent structure may not extend over the entire surface of the absorbent system, and may be configured to provide an intake layer portion which is additional to the high saturation, wicking layer region. This arrangement can locate the intake layer region to be in a substantially direct contact with the incoming liquid, and thereby allow a more immediate access to the incoming liquid and an improved, liquid intake function.
In additional aspects, at least one primary layer region can have a non-uniform, selectively zoned basis weight distribution. Particular configurations of the at least one primary layer region can be constructed with a target area of the primary layer region having a basis weight which is less than a basis weight of another non-target portion of the primary layer region. Moreover, at least one primary layer region can have a heterogeneous structure. In particular configurations, the at least one primary layer region can include a plurality of two or more sublayers.
In other aspects of the invention, the layer regions of the absorbent system can cooperate to provide a desired Liquid Wicking Potential value, such as a Liquid Wicking Value of at least about 16%. The invention can also provide a desired Flow Conductance Value, such as a Flow Conductance Value of at least about 7*10xe2x88x926 cm3. In additional aspects, the invention can provide a combined Conductance-Wicking value of at least about 14*10xe2x88x926 cm3. Further aspects of the invention can provide a system which provides the desired Flow Conductance Value and also includes at least one layer region having the desired Liquid Wicking Value. Still other aspects of the invention can include superabsorbent polymer (SAP) material which exhibits a particular controlled absorbency rate. For example, a desired controlled-rate superabsorbent can exhibit a particular absorbency rate, Tau value, such as a Tau value of at least about 0.67 min. In additional aspects, the invention can include a combination of superabsorbent materials which have a particular ratio of Tau values.
In its various aspects, the present invention can provide an article having a more efficient absorbent structure which is thin with low bulk, has high absorbent capacity, and is resistant to leakage. The configurations of the invention can more fully utilize the total potential absorbent capacity of the absorbent structure, and can more efficiently move and distribute acquired liquid away from the original intake area to more remote areas which are located closer to the distal end regions of the absorbent structure. In addition, the structures of the invention can provide an ability to acquire and intake liquid at a rapid rate, and can maintain the desired intake rate after the absorbent structure has been wetted and has reached a significant portion of its potential, total absorbent capacity.